A device for a three-dimensional image display is classified as a glasses type using special glasses and a non-glasses type without using any type of glasses (autostereoscopic display). The glasses type three-dimensional display device using the special glasses (e.g., polarized glasses) was commercialized prior to the autostereoscopic displays. However, the glasses type is disadvantageous since it required the use of special glasses. Thus, a portion of the autostereoscopic display device will gradually increase. On the other hand, the autostereoscopic display is disadvantageous since it is possible that a crosstalk between viewing zones and a pseudo-stereoscopic vision may occur. As such, in the non-glasses type, it is not easy to display natural three-dimensional images when an observer moves.
Referring to FIG. 1, the problems of conventional technologies are explained through a typical autostereoscopic display device using a parallax barrier in a three-dimensional image screen having two viewpoints. In a display panel DP, images for left and right eyes are displayed alternately by pixel units along a horizontal direction. A barrier substrate BS having barriers and apertures alternately is disposed apart from the display panel DP at a predetermined distance. The barrier substrate BS is designed considering a pixel size and an optimal viewing distance. The observer positioned at optimal observation points from the barrier substrate BS may observe images for the left eye through the left eye and images for the right eye through the right eye. In case of FIG. 1, when the left eye of the observer is positioned at A and the right eye is positioned at B, the observer may be positioned at the optimal observation point. The optimal observation points are repeatedly located apart from each other at a predetermined distance F along a horizontal direction. The optimal observation points are positioned apart from the display panel DP at a predetermined distance. For example, the predetermined distance F may be an average distance, i.e. 65 mm, between the left and right eyes of an adult. The typical autostereoscopic display apparatus may utilize a micro lenticular lens periodically arranged optical substrate instead of the barrier substrate BS.
The autostereoscopic display device is advantageous since there is no need to wear glasses to see three-dimensional images. However, it is disadvantageous since it is possible that the crosstalk between viewing zones and pseudo-stereoscopic vision may occur when the observer moves. Theoretically, when the images for the left eye are only projected into the left eye and the images for the right eye are only projected into the right eye, the observer can observe precise three-dimensional images. The crosstalk refers to an incomplete isolation of left and right eye channels so that one leaks into the other. That is, the images for the left and right eyes are mixed and projected into the left and right eyes. Referring to FIG. 1, when the observer's left eye moves from A to D, the observer's right eye moves from B to E. Then, the images for the left and right eyes are mixed and projected into the left and right eyes. The crosstalk may occur between the optimal observation points for the left and right eyes. The crosstalk is maximized at the intermediate of the optimal observation points for the left and right eyes.
At the three-dimensional image display device using binocular disparity means, a region of the pseudo-stereoscopic vision exists between main viewing zones and sub viewing zones. The region of the pseudo-stereoscopic vision represents a region that the images for the left eye are projected into the right eye and the images for the right eye are projected into the left eye. This is so that the observer may observe a distorted three-dimensional image instead of the precise three-dimensional image. Referring to FIG. 1, when the observer's left eye is positioned at B and the observer's right eye is positioned at C, the pseudo-stereoscopic vision may occur.
When designing the three-dimensional image display device, a distance between the left and right eyes is typically regarded as an average value, i.e., 65 mm, although the distance between the left and right eyes may differ from the average value and vary according to the observers. For example, the distance between the left and right eyes varies according to the classification of humans, e.g., children, men, women and the like. Furthermore, the distance between the left and right eyes varies according to each one included in the classification of the humans. If the left and right eyes get out of the optimal observation point, then the crosstalk may occur. In case that the distance between the left and right eyes is much different from the average value, no matter how well the left and right eyes are fitted into the optimal observation point, the crosstalk would occur. As such, the observer cannot observe the three-dimensional image precisely. The crosstalk and the pseudo-stereoscopic vision are problems of a conventional three-dimensional image display device using the parallax barrier and the lenticular lens. To solve the problems of the conventional three-dimensional image display device, a variety of methods that change a design of the optical substrate according to a characteristic of the three-dimensional image display device have been studied. However, such methods could not completely eliminate the crosstalk.